Surfaces containing coupling activator compounds and reinforced composites produced therefrom

ABSTRACT

The invention relates to products and processes employing coupling activator compounds represented by the following formula I: 
       S—X-A  (I) 
     wherein S represents a silane coupling moiety capable of bonding with the surface of an inorganic substrate, A represents a ring-opening polymerization activator moiety, or blocked precursor thereof, and X represents a linking moiety. Substrates containing the coupling activator compounds are useful in preparing reinforced resins.

BACKGROUND OF THE INVENTION

It is well-known to employ inorganic materials in composite articles tostrengthen and reinforce the articles. In addition to increaseddimensional stability, addition of the inorganic material providespolymer composites with significantly improved physical and mechanicalproperties. As one example, glass fibres may be placed into a polymermatrix where the high tensile strength of glass causes the composite tobecome more rigid. The glass fibres incorporated in the polymer matrixmay take various forms: continuous or chopped strands, rovings, woven ornon-woven fabrics, continuous or chopped strand mats, etc.

Conventionally, glass fibres are formed by attenuating streams of amolten glass material from a bushing or orifice. The glass fibres may beattenuated by pulling by a winder, which collects filaments into apackage or by other equipment or method capable of pulling the fibres. Asizing composition, or chemical treatment, is typically applied to thefibres after they are drawn from the bushing. After the fibres aretreated with the sizing, which is typically in aqueous form, they may bedried in a package, chopped, or kept in the wet state before downstreamprocessing.

Fibreglass may be mixed with a polymeric resin in an extruder andsupplied to a compression- or injection-moulding machine to be formedinto glass fibre-reinforced plastic composites. Typically, polymerpellets and fibreglass are fed together or separately into an extruder.During the extrusion process using single or twin-screw machines, theresin is melted and the fibres are dispersed throughout the molten resinto form a fibre/resin mixture. Next, the fibre/resin mixture may bedegassed, cooled, and formed into pellets. The dry fibre strand/resindispersion pellets are then fed to a moulding machine and formed intomoulded composite articles that have a substantially homogeneousdispersion of glass fibre strands throughout the composite article.

Alternatively, in the process using continuous filaments, fibreglassfilaments are mixed with the molten resin in an extruder with the screwgeometry designed to mix the matrix with fibres without causingsignificant damage to the fibres. Obtained extruded materials are thensubjected to compression moulding to form long-fibre reinforcedthermoplastic materials with significantly improved mechanicalproperties due principally to the fibres having a higher aspect ratio.

Various chemical treatments exist for inorganic surfaces such as glassfibres to aid in their processability and applications. After fibreformation and before bundling, the filaments or fibres may be treatedwith a coating composition (hereinafter referred to as a “sizingcomposition”) that is applied to at least a portion of the surface ofthe individual filaments to protect them from abrasion, improve thechemical or physical bonding, and to assist in processing. As usedherein, the term “sizing composition”, refers to any such coatingcomposition applied to the filaments after forming. Sizing compositionsmay provide protection for subsequent processing steps, such as thosewhere the fibres pass by contact points as in the winding of the fibresand strands onto a forming package, drying the sized fibres to removethe water and/or other solvent or melting of the film former on thefibre surface, twisting from one package to a bobbin, beaming to placethe yarn onto very large packages ordinarily used as the warp in afabric, chopping in a wet or dry condition, roving into larger bundlesor groups of strands, unwinding, and other downstream processes. Inaddition, sizing compositions can play a dual role when placed on fibresthat reinforce polymeric matrices in the production of fibre-reinforcedplastics. In such applications, the sizing composition can provideprotection as well as compatibility and/or chemical bonding between thefibre and the matrix polymer. Conventional sizing compositions typicallycontain one or more film forming polymeric or resinous components,glass-resin coupling agents, and one or more lubricants dissolved ordispersed in a liquid medium. The film forming component of the sizingcomposition is desirably selected to be compatible with the matrix resinor resins in which the glass fibres are to be embedded.

Many types of polymers may be reinforced by inorganic materials. Ofparticular note are those polymers formed by ring-opening polymerizationreactions. Polyamides (PA), such as poly(caprolactam), commonly know as“Nylon-6” or “polyamide-6”, are examples of resins formed byring-opening polymerization that are frequently reinforced by glassfibres. There is a need to provide glass-reinforced polyamide compositeswith high glass loading; however, one of the barriers is the highpolymer viscosity of the polyamide in the molten state. This highviscosity hinders the dispersion of the glass fibres throughout themolten resin when the fibre/resin mixture is formed.

Anionic-catalysed ring-opening polymerization of lactams has become acommercially significant method for preparation of PA resins since thesepolymerizations can be conducted at relatively low temperatures andunder atmospheric pressures. Caprolactam is by far the most studiedlactam for such reactions and Nylon-6 prepared by this route comparesfavorably in properties with that prepared by conventional hydrolyticpolymerization. Fast reaction kinetics, absence of by-products, and thecrystalline nature of the Nylon so produced also makes anionicpolymerization of lactams a compelling choice for several industrialapplications, including reactive extrusion, reactive thermoplasticpultrusion, reaction transfer molding, D-LFT, compression and injectionmolding, and reaction injection molding.

In its various embodiments, the present invention combines the processesof forming and loading the inorganic component of a reinforced resinwith the ring-opening polymerization of a suitable monomer. Theinvention thereby overcomes any high viscosity issue associated withcombining fibres with resins, provides improved interfacial adhesionbetween the polymer matrix and the inorganic reinforcing material, andthereby provides improved composite materials.

BRIEF SUMMARY OF THE INVENTION

In one embodiment, the invention provides an inorganic substrate, forexample glass fibres in the form of continuous strands, chopped strands,rovings, mats, etc., having bonded thereto a “coupling activator”compound of the following formula I:

S—X-A  (I)

wherein S represents a silane coupling moiety through which the compoundis bonded to the inorganic substrate, A represents a ring-openingpolymerization activator moiety, or a blocked precursor thereof, and Xrepresents a linking moiety capable of linking the S moiety and the Amoiety. The polymerization activator moiety or precursor is capable ofparticipating in an in situ ring-opening polymerization of a monomer inthe presence of a polymerization catalyst when exposed to ring-openingpolymerization conditions. As a result, the inorganic substrate of theinvention may be used as a ring-opening polymerization activator, aloneor with conventional polymerization activators, in the formation ofpolymers that are reinforced with the inorganic material. As examples ofinorganic substrates, mention may be made of glass, basalt, carbonfibres, carbon nanotubes, inorganic nanotubes, and metal fibres. For thepurposes of the present invention, carbon nanotubes and carbon fibresare inorganic substrates. Glass substrates of the invention areparticularly useful in the formation of glass-reinforced polyamides.

The surface of the substrate of the invention may contain a coating of asizing composition comprising a coupling activator compound of formula Iabove. In one embodiment of the invention, silane-functionalizedisocyanate may be blocked with caprolactam to produce2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide, which canparticipate in the anionic ring-opening polymerization of caprolactammonomer.

Blocked precursors of coupling activator compounds may includeisocyanates blocked with compounds other than the activator compound.Under the processing conditions, such blocked isocyanate would becomeunblocked to furnish free isocyanate. The isocyanate may, under thereaction conditions, become blocked with the monomer thus forming thepolymerisation activator. The silane functionality of the isocyanatecompound may react with the substrate, such as glass, thus leading toimproved interfacial adhesion.

In another embodiment, the invention provides a process for preparing areinforced resin material, e.g. a glass-reinforced resin polyamide. Asizing composition comprising a coupling activator compound of formula Iabove may be applied to a glass substrate. In one embodiment, the sizedglass substrate may be mixed with a lactam monomer, e.g. caprolactam,and a polymerization catalyst to form a polymerization mixture that maythen be exposed to conditions sufficient to cause an in situ anionicring-opening polymerization of the lactam monomer. In anotherembodiment, the sized glass substrate may be mixed with a cyclic olefinmonomer, e.g. norbornene, and a polymerization catalyst to form apolymerization mixture that may then be exposed to conditions sufficientto cause an in situ ring-opening metathesis polymerization of the cyclicolefin monomer. The resulting composite products comprise a matrix inwhich the glass substrate is grafted onto the polymer, therebysubstantially improving the coupling between the glass and the polymer.This improved coupling is expected to provide tougher compositematerials.

In other embodiments, the invention provides processes for forming areinforced resin material into a solid mass of a prescribed shape andsize by conventional processing procedures, e.g. reactive extrusion,resin transfer molding, pultrusion, reaction injection molding, or anyother suitable process.

These and other embodiments of the present invention are described ingreater detail in the detailed description of the invention whichfollows.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to products and processes employing certaincompounds referred to herein as “coupling activator” compounds becausethey serve both a coupling and a ring-opening polymerization function.In general terms, coupling activator compounds of the invention may berepresented by the following formula I:

S—X-A  (I)

wherein S represents a silane coupling moiety capable of bonding to thesurface of an inorganic substrate, A represents a ring-openingpolymerization activator moiety or a blocked precursor thereof, and Xrepresents a linking moiety capable of linking the S moiety and the Amoiety. As examples of suitable X moieties, mention may be made ofalkyl, aryl, and alkyl-aryl groups. The linking group X may be of anylength, including null, in which case the activator moiety A would bedirectly attached to the silane S.

The silane coupling moiety S may comprise any of the known functionalgroups that react with the surface of an inorganic substrate, e.g. anorganosilane group. Compounds containing organosilane groups are wellknown coupling agents in material systems that consist of an inorganic(e.g. glass) and organic (e.g. polymer) phase, and serve to covalentlybond the organic groups in the compound to groups on the inorganicsurface. As one example, S may comprise an organosilane group of thefollowing formula II:

wherein X is as defined in Formula I above; and R¹, R² and R³ may be thesame or different and each may represent alkyl, aryl, alkoxy, halogen,hydroxy, or a cyclic structure wherein X is connected with one or moreof R¹, R², and R³.

The ring-opening polymerization activator moiety A may be any knownorganic reactive group that participates in a ring-openingpolymerization reaction, which term includes anionic ring-openingpolymerization, cationic ring-opening polymerization and ring-openingmetathesis polymerization (ROMP). For example, such reactive group mayparticipate in the polymerization by forming a reactive center wherefurther cyclic monomers can join after opening to provide a largerpolymer chain through ionic propagation.

In one embodiment, the A moiety may be a group that serves the functionof an activator in the anionic ring-opening polymerization of a lactamor a lactone, e.g. A may be an N-substituted imide group. Suchpolymerizations are well-known in the art and will not be discussedherein in great detail. If further reference is needed, thesepolymerization reactions are discussed more completely in the patentliterature, e.g. in U.S. Pat. Nos. 3,621,001; 4,188,478; 5,864,007;6,579,965; and the patents cited therein, all of which are incorporatedby reference herein. Generally, these polymerizations are conducted atlow temperatures (80-160° C.), below the melting point of the resultingpolyamides (which is typically above 200° C.), and typically employ, inaddition to the activator compound, two other components; i.e.: a lactammonomer and a polymerization catalyst. The monomer component may be alactam or lactone having from 3 to 12 carbon atoms in the main ring,such as caprolactam and caprolactone. The polymerization catalyst may bean alkali metal salt of the lactam or lactone monomer, such as sodiumcaprolactam and sodium caprolactone. There may also be other knownauxiliary components in the polymerization mixture (e.g. co-initiators,catalysts, co-catalysts, electron donors, accelerators, sensitizers,processing aids, release agents, etc.).

In the anionic ring-opening polymerization of the lactam or lactonemonomer, the combination of monomer and polymerization catalyst producesa catalyzed monomer species containing an atom with a reactive freeanion. As used herein, the term “ring-opening polymerization activator”may be used to denote this catalyzed monomer species, and the term“ring-opening polymerization activator moiety” may be defined as a groupthat reacts with the catalyzed monomer molecule to cleave the lactamring and start the initial growth of the polymeric chain. In oneembodiment the polymerization catalyst may comprise an alkali metal saltof the lactam or lactone and the activator moiety may comprise anN-substituted imide group, e.g. an N-acyl lactam group.

As another example, in the ring-opening metathesis polymerization (ROMP)of a cyclic olefin monomer such a norbornene, cyclopentadiene,cyclooctadiene, decyclopentadiene, etc., the A moiety of the compound ofFormula I above may be a cyclic olefin-substituted imide group thatundergoes ROMP under catalytic conditions using an alkylidene catalystsuch as developed by R. R. Schrock or R. Grubbs. In this case the Amoiety becomes part of the polymer chain.

As specific examples of coupling activator compounds of Formula I abovethat are useful in the anionic ring-opening polymerization of lactams,mention may be made of certain N-propylsilyl-N′-acyl-ureas described inU.S. Pat. No. 4,697,009, incorporated by reference herein. In oneembodiment, the coupling activator compound may comprise2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide.

In one embodiment, the coupling activator compounds of the invention maybe prepared in accordance with the process set forth in theaforementioned incorporated U.S. Pat. No. 4,697,009. For example, thecoupling activator compounds may be prepared by mixing in an aprotic,polar organic solvent such as N,N-dimethylformamide equimolar amounts ofan alkali isocyanate (e.g. sodium isocyanate or potassium isocyanate), a3-halopropyl silane (e.g. 3-chloropropyltriethoxysilane) andcaprolactam, and reacting the ingredients with each other at elevatedtemperature. At the end of the reaction and cooling the mixture to roomtemperature, the precipitated alkali halide may be filtered off and thesolvent may be removed from the filtrate to obtain the desired blockedisocyanate compound. Alternatively, coupling activator compounds may beprepared according to the procedure described in International PatentNo. WO 2006/012957, incorporated herein by reference

In another embodiment, the coupling activator,2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide may be preparedin accordance with the following reaction scheme A:

1.1 eq. of caprolactam 1 may be mixed with 1.0 eq. of3-isocyanatopropyltriethoxysilane 2 and the mixture heated at 80-100° C.until the completion of the reaction and formation of2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide 3. The reactionprogress can be measured by FT-IR, where disappearance of the isocyanatepeak at 2300 cm⁻¹ should be observed. The reaction may be run neat or insolution, with 1,4-dioxane as the solvent. Organotin catalyst (e.g.dibutyltin dilaurate) may be used to significantly improve the reactionrate.

In one embodiment, a coupling activator compound of the invention may beused as the sole initiator in a anionic ring-opening polymerizationreaction, or may be used in combination with other known initiatorcompounds. For example, compound 3 above may be used as the initiator inthe reactive extrusion of Nylon-6 in accordance with the followingreaction scheme B:

In the above reaction, 97.5 wt % of caprolactam 1 may be mixed with 1.5wt % of the polymerization catalyst sodium caprolactam 4, and 1.0 wt %of 2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide 3. Themixture may be fed into a zone 2 of a 15-zone, L/D=60 Leistritzco-rotating 27-mm twin-screw extruder with temperature profile of80-205° C. at the screw speed of 78 min⁻¹ at torque of 4.8-9.6 MPa toaccomplish ring-opening polymerization and obtain Nylon-6.Alternatively, the same results may be achieved by running the reactionin a beaker instead of using the reactive extrusion process.

In another embodiment, a coupling activator compound of the inventionmay participate in a ROMP reaction such as shown in the followingreaction scheme C:

In this case, norbornene-substituted maleic anhydride 6 may be reactedwith γ-aminopropyltriethoxysilane 7 to provide a substituted imidecoupling activator compound 8. Coupling activator compound 8 can thenundergo ring-opening metathesis polymerization (typically undercatalytic conditions using rhodium, rhenium, or molybdenum alkylidenecatalysts such as were developed by Grubbs or Schrock). Monomers such ascyclopentadiene, cyclooctadiene, dicyclopentadiene, norbornene or othermonomers suitable for ROMP may be used to yield polymers such asillustrated by compound 9.

In another embodiment, the invention provides an inorganic substratehaving bonded thereto a coupling activator compound of Formula I above.The inorganic substrate may comprise a plurality of glass fibres whereinat least one glass fibre is at least partially coated with the residueof a sizing composition comprising the coupling activator compound. Aspreviously described, the silane coupling moiety S of the couplingactivator compound that is included in the coated sizing composition maycovalently bond to the glass fibre when the composition is coated anddried on the glass substrate, thereby securely attaching the couplingactivator compound to the glass substrate.

Some embodiments of glass fibres according to the present invention maybe particularly suited for reinforcing polyamide resins. Polyamideresins reinforced with glass fibres in accordance with the invention maycomprise Nylon 6, Nylon 6:6, Nylon 6:12, Nylon 4:6, Nylon 6:10, Nylon12, polyamide 6T (polyhexamethylene terephthalamide), polyamide 6I(polyhexamethylene isophthalamide) or mixtures thereof. In oneembodiment, the A moiety of the coupling activator compound in formula Iabove may comprise a blocked precursor of the active activator moiety,e.g. a blocked isocyanate. In this embodiment, the precursor compoundmay be coated on the glass substrate and the active form of theactivator may be generated in situ on the surface of a glass substratewhen exposed to unblocking conditions. This process may be illustratedby the reaction scheme D below:

The blocked isocyanate group may be obtained by reacting the isocyanategroup of compound 2 in reaction scheme A above with a compound thatrenders the isocyanate group unreactive. A suitable blocking agent forthe isocyanate group may be determined by its ability to prevent theblocked isocyanate from reacting until a desired temperature isachieved. Examples of compounds that may be suitable blocking agentsinclude, but are not limited to, oximes such as methyl ethyl ketoxime,acetone oxime, and cyclohexanone oxime, lactams such as ε-caprolactam,and pyrazoles. Organosilicon compounds with a blocked isocyanate groupare known in the art, e.g. see U.S. Patent Publication 2007/0123644,incorporated herein by reference. Upon heating or other deblockingconditions, these blocked isocyanates decompose to free isocyanate andthe blocking species. Deblocking temperatures depend on the blockinggroups and typically are in the range 70-200° C. The blocked isocyanatemay be included as a component of the sizing composition used to sizeglass fibres, and may be applied to glass fibres in the mannerpreviously described to form the entity identified as “blocked 2 onglass” in reaction scheme D above. When the glass fibres with blockedisocyanate compound are exposed to unblocking conditions, e.g. elevatedtemperatures during processing, the isocyanate group may becomeunblocked to form the active isocyanate compound 2 chemically bonded tothe glass surface. Now unblocked, the isocyanate group is available toreact with the caprolactam monomer 1 in reaction scheme A above, therebyforming coupling activator compound 3 bonded to the glass surface. Thecoupling activator compound may then enter into the in situpolymerization reaction on the surface of the glass fibres in accordancewith the invention. If the isocyanate is blocked with a monomer in thepolymerization reaction; e.g. when the isocyanate is blocked bycapolactam in the anionic ring-opening polymerization of caprolactam,the blocked isocyanate may not need to dissociate into the freeisocyanate in order to facilitate the ring-opening polymerizationreaction.

Sizing compositions suitable for the present invention may be preparedby adding a coupling activator compound of formula I to water or othersuitable solvent to form a solution. The sizing composition may alsoinclude other sizing composition components known in the art, e.g.film-forming polymers, lubricants, defoamers, biocides, other silanes,etc. The sizing composition should contain an amount of couplingactivator compound sufficient to accomplish the desired participation inthe ring-opening polymerization. The overall concentration of thecoupling activator compound and other components in the sizingcomposition can be adjusted over a wide range according to the means ofapplication to be used, the character of the inorganic reinforcingmaterial to be sized, and the intended use of the sized inorganicreinforcing material. In one embodiment, the sizing composition maycontain about 5 wt % of the coupling activator compound. The componentsmay be added sequentially, or they may be pre-diluted before they arecombined to form the sizing composition.

The sizing composition may be applied to the inorganic substrate bysuitable methods known to one of skill in the art. For example, thesizing composition may be applied to glass fibres pulled from a bushingusing a kiss-roll applicator. Other ways of applying the sizingcomposition may include contacting glass fibres with other static ordynamic applicators, such as a belt applicator, spraying, dipping, orany other means. Alternatively, the coupling activator compound may beadded to the binder used in the process of forming woven or non-wovenmats.

After the sizing has been applied, fibres may be collected in rovings ormay be chopped to form chopped strands. Rovings of continuous sizedstrands may be used in some applications, e.g. in long-fibrethermoplastics, or the rovings may be comingled and may be later choppedto a desired length. The length and diameter of the chopped glass fibresused for reinforcing polyamide resins may be determined by variousfactors such as, but not limited to, the ease of handling when glassfibres are melt-kneaded with a polyamide resin, the reinforcing effectof the glass fibres, glass fibre dispersing ability, the type ofpolyamide resin in which the chopped glass fibre will be used toreinforce and the intended use of a glass-reinforced polyamide resinarticle. In some embodiments, the length of the chopped glass fibrestrand may have a lower limit of 1 mm and an upper limit of length of 50mm. In one embodiment suitable for reinforcement of Nylon-6, the lengthof the strand may be about 6 mm. After the fibre strands have beenchopped, they may then be dried until the moisture level of the fibresis sufficiently low, e.g. below 0.1%.

Non-limiting examples of glass fibres suitable for use in the presentinvention can include those prepared from fibresable glass compositionssuch as “E-glass”, “A-glass”, “C-glass”, “S-glass”, “ECR-glass”(corrosion resistant glass), “T-glass”, and fluorine and/or boron-freederivatives thereof. Typical formulations of glass fibres are disclosedin K. Lowenstein, The Manufacturing Technology of Continuous GlassFibres (Third Ed. 1993), incorporated herein by reference.

The invention further provides reinforced resin materials and processesfor preparing them from an inorganic substrate that has bonded theretocoupling activator compounds of the present invention. In oneembodiment, a sizing composition comprising the coupling activatorcompound of Formula I may be applied to a glass substrate, the sizedglass substrate may be mixed with a lactam monomer and a polymerizationcatalyst to form a polymerization mixture; and the mixture may beexposed to conditions sufficient to cause an in situ anionicring-opening polymerization of the lactam monomer, thereby forming apolymer/glass matrix in which the glass substrate is grafted to thepolyamide polymer. The polymerization is referred to as “in situ”because the polymer is formed directly on the surface of the glasssubstrate, as opposed to being first formed and then coated on the glasssurface. As a result, the coupling of the glass component and thepolymer component of the composite material is substantially improvedover prior art glass-reinforced resins.

Reinforced resin materials of the invention may be produced usingwell-known processing procedures such as reactive extrusion, resintransfer molding, pultrusion, reaction transfer molding, D-LFT,compression and injection molding, and reaction injection molding.Example 1 below illustrates the production of glass-reinforcedpolyamide-6 using the process of the invention in a reactive extrusionprocess, and for comparative purposes, Example 2 below illustrates theproduction of a glass-reinforced polyamide-6 using a conventionalreactive extrusion process:

Example 1

Chopped fibre strands sized with a sizing composition comprising2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide (compound 3 inreaction scheme A above) may be fed into an extruder as previouslydescribed. A monomer mix comprising caprolactam monomer 1 and sodiumcaprolactam catalyst 4, as shown in reaction scheme B above, may also befed into the extruder to be mixed and heated with the sized glassfibres. The processing conditions within the extruder initiate andcomplete an anionic ring-opening polymerization of caprolactam 1 inaccordance with reaction scheme B, and strands of the resultingglass-reinforced Nylon-6 may be extruded through the extruder die. Asample strand of the glass-reinforced Nylon-6 may be broken undertension. The breaking point may be analyzed with a Scanning ElectronMicroscope (SEM) to show the outstanding coupling of glass and polymerin the composite material provided by the present invention.

Example 2

Chopped glass fibres strands may be sized with a conventional sizingcomposition comprising 0-30 wt % of γ-aminopropyltriethoxysilane orother suitable silane coupling agent, 20-70 wt % of a polyurethaneemulsion or a suitable mixture of emulsions, and 10-50 wt % of alubricant or mixture of lubricants, and 0-50 wt % of any other requiredor preferred additives. The chopped sized fibres may be fed into thesame extruder used in Example 1 above. Referring to reaction scheme Ebelow, monomer mix comprising caprolactam monomer 1, sodium caprolactamcatalyst 4 and a commercially-available activator 5 may also be fed intothe extruder, thereby mixing and heating the mix with the sized glassfibres. The processing conditions within the extruder initiate andcomplete an anionic ring-opening polymerization of the caprolactammonomer 1 within the extruder in accordance with reaction scheme Ebelow:

Strands of the resulting Nylon-6 may then be obtained from the extruderdie and analysis of the breaking point of a broken strand may beperformed to show only average coupling between the glass and thepolymer matrix. The comparison between the products of Examples 1 and 2clearly demonstrate the unexpected and superior results achieved by thepresent invention.

In another embodiment, substrates of the present invention may be usedin a resin transfer molding process. For example, glass or other fibresor fibrous mats or fabrics, may be placed in a closed mold and a mixturecomprising lactam monomer and polymerization catalyst may be transferredinto the mold to form a polymerization mixture. The mold walls may beheated to a temperature sufficient to cause ring-opening polymerizationof the monomer and result in the formation of the glass-reinforced resinmaterial in the mold shape. The mold may then be opened to provide ashaped glass-reinforced resin article. In another embodiment, thepresent invention may be used to simplify the preparation of woven ornon-woven fabric laminates using vacuum-assisted resin transfer molding.These materials may be used to make high-end composites for applicationssuch as wind turbine blades, automotive or aircraft parts, andreinforced pressure vessels. Current processes typically utilize atwo-component application wherein a first molten mixture comprisinglactam monomer and polymerization catalyst and a second molten mixturecomprising lactam monomer and activator compound are separately mixedwith glass fibres containing conventional sizing. In a vacuum-assistedresin transfer molding process utilizing the present invention, only onemixture comprising lactam monomer and polymerization catalyst may beused to cover glass fibres containing a coupling activator compound ofFormula I.

In another embodiment, the process of the invention may comprise usingthe sized substrates in a pultrusion process. For example, glass fibrescontaining a coupling activator compound of Formula I may be pulled froma creel through a bath comprising a composition of lactam monomer andpolymerization catalyst to impregnate the fibres. The impregnated glassfibres may then enter a heated die that has been machined to the finalshape of the article to be produced. While the impregnated glass fibresare being pulled through the die, the heat causes polymerization of thelactam monomer and the formation of the glass-reinforced resin, whichexits the die in the desired shape. The shaped resin may then be cut tothe desired length.

In still another embodiment, the process of the invention may compriseusing substrates containing a coupling activator compound of Formula Iin a reaction injection molding process. For example, glass fibres sizedwith a compound of Formula I may be dispersed in a liquid compositioncomprising lactam monomer and polymerization catalyst. The liquidcomposition may then be injected into a mold and heated to cause anionicring-opening polymerization of the lactam monomer. After polymerizationis completed, the shaped glass-reinforced resin may be removed from themold.

One skilled in the art can easily ascertain the essentialcharacteristics of this invention from the foregoing description, andwithout departing from the spirit and scope thereof, can make variouschanges and modifications of the invention to adapt it to various usagesand conditions.

1. An inorganic substrate having bonded thereto a coupling activator compound of the formula: S—X-A wherein S represents a silane coupling moiety through which the compound is bonded to the surface of the inorganic substrate, A represents a ring-opening polymerization activator moiety, or blocked precursor thereof, which is capable of participating in an in situ ring-opening polymerization of a monomer in the presence of a polymerization catalyst when exposed to ring-opening polymerization conditions, and X represents a linking moiety capable of linking the S moiety and the A moiety.
 2. An inorganic substrate according to claim 1 wherein the surface of the inorganic substrate contains a coating of a sizing composition comprising the coupling activator compound.
 3. An inorganic substrate according to claim 1 wherein the inorganic material is glass, basalt, carbon fibres, carbon nanotubes, inorganic nanotubes, or metal fibres.
 4. An inorganic substrate according to claim 3 wherein the glass is in the form of one or more continuous strands, chopped strands, mats or rovings.
 5. An inorganic substrate according to claim 1 wherein S represents an organosilane group of the formula:

wherein X is as defined in claim 1, and R¹, R² and R³ may be the same or different and each may represent alkyl, aryl, alkoxy, halogen, hydroxy, or a cyclic structure wherein X is connected with one or more of R¹, R² and R³.
 6. An inorganic substrate according to claim 1 wherein the coupling activator compound is 2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide.
 7. An inorganic substrate according to claim 1 wherein A represents an N-substituted imide group.
 8. An inorganic substrate according to claim 1 wherein X represents alkyl, aryl, or alkyl-aryl.
 9. An inorganic substrate according to claim 1 wherein A is a blocked isocyanate group.
 10. A process for preparing a reinforced resin material comprising the steps of: providing an inorganic substrate; applying to the inorganic substrate a sizing composition comprising a coupling activator compound of the formula: S—X-A wherein S represents a silane coupling moiety capable of bonding with the surface of the inorganic substrate, and A represents a ring-opening polymerization activator moiety, or blocked precursor thereof; which is capable of participating in an in situ ring-opening polymerization of a monomer in the presence of a polymerization catalyst when exposed to ring-opening polymerization conditions, and X represents a linking moiety capable of linking the S moiety and the A moiety; mixing the sized inorganic substrate with a monomer and a ring-opening polymerization catalyst to form a polymerization mixture; and exposing the polymerization mixture to conditions sufficient to cause an in situ ring-opening polymerization of the monomer to form a reinforced resin in which the inorganic substrate is grafted onto a polymer.
 11. A process according to claim 10 wherein the monomer is a lactam or lactone having 3-12 carbon atoms in the main ring, and the polymerization is anionic ring-opening polymerization.
 12. A process according to claim 10 wherein the monomer is a cyclic olefin and the polymerization is ring-opening metathesis polymerization.
 13. A process according to claim 10 wherein A is a blocked isocyanate group that becomes unblocked to form an active isocyanate group that reacts with the monomer to form the polymerization activator moiety when exposed to the polymerization conditions.
 14. A process according to claim 10 wherein the sizing composition is coated on the surface of glass fibres and the sized glass fibres are collected in the form of rovings.
 15. A process according to claim 10 comprising a reactive extrusion process wherein sized fibres and a composition comprising monomer and catalyst are separately fed into an extruder to form the polymerization mixture, the polymerization mixture is exposed to polymerization conditions in the extruder to cause the polymerization, and the resultant fiber reinforced resin is extruded through a die into the desired shape.
 16. A process according to claim 10 comprising a resin transfer molding process wherein sized fibres and a composition comprising monomer and catalyst are mixed together in a closed mold to form the polymerization mixture, the polymerization mixture is exposed to the polymerization conditions in the mold to cause the polymerization, the mold is opened, and the resultant shaped fiber reinforced resin is removed from the mold.
 17. A process according to claim 10 comprising a pultrusion process wherein sized fibres are pulled through a composition comprising monomer and catalyst to impregnate the fibres with the composition and form the polymerization mixture, the impregnated fibres are pulled through a heated die to cause the polymerization, and the resultant shaped fiber reinforced resin is recovered from the die.
 18. A process according to claim 10 comprising a reinforced reaction injection molding process wherein sized fibres are dispersed in a liquid composition comprising monomer and catalyst, the liquid composition is injected into a mold, heated to cause the polymerization, and the resultant shaped fiber reinforced resin is removed from the mold.
 19. A fiber reinforced resin material formed by the process of claim
 10. 20. An inorganic substrate having bonded thereto 2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide or a blocked isocyanate precursor thereof.
 21. A polymerization mixture for preparing a fibreglass-reinforced polyamide comprising: inorganic substrate having coated on the surface thereof a sizing composition comprising a coupling activator compound of the formula: S—X-A wherein S represents a silane coupling moiety capable of bonding to the inorganic substrate surface; A represents an anionic ring-opening polymerization activator moiety or a blocked precursor thereof; and X represents an alkyl, aryl or alkyl-aryl linking moiety; a lactam or lactone monomer; and a catalyst.
 22. A process for preparing fibreglass-reinforced Nylon-6 comprising the steps of: preparing a sizing composition comprising 2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide; coating the sizing composition on the surface of rovings of glass fibres; drying the sized rovings; mixing the sized rovings with a caprolactam monomer and sodium caprolactam catalyst to form a polymerization mixture; and heating the polymerization composition to a temperature sufficient to cause an in situ anionic ring-opening polymerization of the caprolactam monomer to form a matrix in which the glass fibres are grafted to Nylon-6 polymer.
 23. A glass-reinforced Nylon-6 formed by the process of claim
 22. 